Epidemiology

• Sex: ♂ > ♀
• Age: more common in children
  • 90% of affected individuals < 10 years
  • Other small vessel vasculitides mainly affect adults

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Etiology

• Preceding infection
  • Up to 90% of cases are preceded by viral or bacterial infection 1–3 weeks prior.
  • Most commonly an upper respiratory tract infection caused by group A Streptococcus
  • IgA nephropathy
  • Drugs

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Pathophysiology

Hypothesized pathophysiological mechanism: exposure to allergen/antigen (e.g., infection, drugs) → stimulation of IgA production → deposition of IgA immune complexes in vascular walls (e.g., in the skin, GI tract, joints, kidneys) → activation of complement → vascular inflammation and damage

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Clinical features

An upper respiratory tract infection often precedes symptom onset by 1–3 weeks.

• Skin (∼ 100% of cases)
  • Symmetrically distributed erythematous papules or urticarial lesions that coalesce into palpable purpura
  • Bullae, pustules, and necrotic or hemorrhagic purpura (more common in adults)
  • Most commonly in the lower extremities, buttocks, and other areas of pressure or constraint (e.g., from clothing)
• Joints (∼ 75% of cases)
  • Arthritis/arthralgia
    • Usually bilateral, self-limited, and nondestructive; children may present with a limp.
  • Most commonly in the ankles and knees
• Gastrointestinal tract (∼ 60% of cases)
  • Colicky abdominal pain
  • Intussusception
  • Hematochezia or melena
  • Nausea and/or vomiting
• Kidneys: IgA nephritis (20–50% of children; 50–80% of adults)
  • Nephritic syndrome

Tip

IgAV is an important differential diagnosis to consider in children with a limp.

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Diagnostics

Biopsy

• IgA and C3 complex deposition (hallmark) in small vessels of the superficial dermis
• ANCA negative vasculitis

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Differential Diagnosis

See Purpura differential diagnosis

Treatment

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